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In upcoming very high-speed wireless LANs (WLANs), the physical (PHY) layer rate may reach 600 Mbps. To achieve high efficiency at the medium access control (MAC) layer, we identify fundamental properties that must be satisfied by any CSMA-/CA-based MAC layers and develop a novel scheme called aggregation with fragment retransmission (AFR) that exhibits(More)
It is well known that the medium access control (MAC) layer is the main bottleneck for the IEEE 802.11 wireless LANs. Much work has been done on performance analysis of the 802.11 MAC. However, most of them assume that the wireless channel is error-free. In this paper , we investigate the saturation throughput performance achieved at the MAC layer, in both(More)
— A Block ACK (BTA) scheme has been proposed in IEEE 802.11e to improve medium access control (MAC) layer performance. It is also a promising technique for next-generation high-speed Wireless LANs (WLANs) such as IEEE 802.11n. We present a theoretical model to evaluate MAC saturation throughput of this scheme. This model takes into account the effects of(More)
We consider the sizing of network buffers in IEEE 802.11-based networks. Wireless networks face a number of fundamental issues that do not arise in wired networks. We demonstrate that the use of fixed-size buffers in 802.11 networks inevitably leads to either undesirable channel underutilization or unnecessary high delays. We present two novel dynamic(More)
A Block Transmission and Acknowledgement (BTA) scheme, also called Block ACK, has been proposed in the IEEE 802.11e wireless LAN (WLAN) specification to improve efficiency of the medium access control layer. The idea of the BTA scheme is to transmit multiple data frames followed by only one acknowledgment frame in a transmission block. In this paper, we(More)
Efficiently sharing spectrum among multiple users is critical to wireless network performance. In this paper, we propose a novel spectrum sharing protocol called Collision-Resistant Multiple Access (CRMA) to achieve high efficiency. In CRMA, each transmitter views the OFDM physical layer as multiple orthogonal but sharable channels, and independently(More)
We consider the medium access control (MAC) layer for very high-speed Wireless LANs, which is designed to support rich multimedia applications such as high-definition television. In such networks, the physical (PHY) layer data rate is proposed to exceed 216Mbps. The legacy MAC layer, however, greatly restricts the performance improvement due to its(More)
Location-based applications (LBAs) are emerging to be the killer applications on mobile devices. To know the whereabouts of devices, various interfaces (<i>ie</i>, GPS, WiFi or cellular) can be used to sense their locations. Ideally, localization should be done all the time. However, keeping any of these interfaces running continuously would drain a(More)